Kim Hyo-Jeong, Sun Yan, Moon Myung-Jin
Department of Biological Sciences, Dankook University, 119 Dandae-ro, Cheonan, 31116, South Korea.
Appl Microsc. 2020 Aug 6;50(1):16. doi: 10.1186/s42649-020-00036-5.
Silk is produced by a variety of insects, but only silk made by terrestrial arthropods has been examined in detail. To fill the gap, this study was designed to understand the silk spinning system of aquatic insect. The larvae of caddis flies, Hydatophylax nigrovittatus produce silk through a pair of labial silk glands and use raw silk to protect themselves in the aquatic environment. The result of this study clearly shows that although silk fibers are made under aquatic conditions, the cellular silk production system is quite similar to that of terrestrial arthropods. Typically, silk production in caddisworm has been achieved by two independent processes in the silk glands. This includes the synthesis of silk fibroin in the posterior region, the production of adhesive glycoproteins in the anterior region, which are ultimately accumulated into functional silk dope and converted to a silk ribbon coated with gluey substances. At the cellular level, each substance of fibroin and glycoprotein is specifically synthesized at different locations, and then transported from the rough ER to the Golgi apparatus as transport vesicles, respectively. Thereafter, the secretory vesicles gradually increase in size by vesicular fusion, forming larger secretory granules containing specific proteins. It was found that these granules eventually migrate to the apical membrane and are exocytosed into the lumen by a mechanism of merocrine secretion.
多种昆虫都能产生丝，但只有陆生节肢动物所产的丝得到了详细研究。为填补这一空白，本研究旨在了解水生昆虫的吐丝系统。毛翅目昆虫黑线沼石蛾的幼虫通过一对唇腺分泌丝，并利用生丝在水生环境中保护自己。本研究结果清楚地表明，尽管丝纤维是在水生条件下形成的，但细胞吐丝生产系统与陆生节肢动物的非常相似。通常，石蛾幼虫的吐丝过程是在丝腺中通过两个独立的过程完成的。这包括在后部区域合成丝素蛋白，在前部区域产生粘性糖蛋白，这些物质最终积累形成功能性丝原液，并转化为涂有粘性物质的丝带。在细胞水平上，丝素蛋白和糖蛋白的每种物质在不同位置特异性合成，然后分别作为运输小泡从粗面内质网运输到高尔基体。此后，分泌小泡通过小泡融合逐渐增大，形成含有特定蛋白质的更大分泌颗粒。研究发现，这些颗粒最终迁移到顶端膜，并通过局部分泌机制分泌到管腔中。
